Thanks folks, much appreciated!
One thing I'm still not sure about though: Should I fill the ragged pulled-out holes first then drill new ones through the filler? Or just squirt resin in the ragged holes and put wall plugs in directly?
I.e. Right now I am thinking to do something like...
I came home to find my shower door has fallen off the wall. As you can see in the pictures it is a heavy glass door, and the wall is made of small tiles on plasterboard. It has to go back in the same place as before as it only just fits in under the sloping ceiling, but I'm not sure how to...